JMJD6 cleaves MePCE to release positive transcription elongation factor b (P-TEFb) in higher eukaryotes

Area of Science:

• Molecular Biology
• Gene Regulation
• Biochemistry

Background:

• Promoter-proximal pausing regulates over 30% of genes in eukaryotes.
• Phosphorylation of RNA polymerase II (Pol II) CTD by P-TEFb is crucial for transcription elongation.
• The mechanism of P-TEFb release from the 7SK snRNP complex is unknown.

Purpose of the Study:

• To elucidate the mechanism of P-TEFb release and recruitment to Pol II CTD.
• To identify the role of Jumonji domain-containing 6 (JMJD6) in transcription regulation.

Main Methods:

• Crystal structure analysis of JMJD6 bound to methyl-arginine.
• In vitro and in vivo enzymatic assays to assess JMJD6's proteolytic activity on MePCE.
• Binding assays and gene expression analysis in mouse and human models.
• Assessment of Pol II CTD phosphorylation following JMJD6 manipulation.

Main Results:

• JMJD6 exhibits a novel proteolytic function, cleaving methylphosphate capping enzyme (MePCE).
• MePCE is a core component of the 7SK snRNP complex, which sequesters P-TEFb.
• JMJD6-mediated MePCE cleavage facilitates P-TEFb release and subsequent recruitment to Pol II CTD.
• Jmjd6 knockout and overexpression studies demonstrate effects on Pol II CTD phosphorylation.

Conclusions:

• JMJD6 disrupts the 7SK snRNP complex by cleaving MePCE.
• JMJD6, with assistance from BRD4, promotes P-TEFb recruitment to Pol II CTD.
• This pathway is critical for productive transcription elongation and gene regulation.